Nacelle anti ice system

ABSTRACT

An anti-icing system of a nacelle inlet of an engine of an aircraft includes first and second direct acting valves and first and second control valve assemblies fluidly connected to the nacelle inlet. The first direct acting valve includes a first inlet, outlet, valve chamber, and piston. The first piston is positioned in the first direct acting valve. The first control valve assembly is fluidly connected to the first valve. The second direct acting valve includes a second inlet, outlet, valve chamber, and piston. The second piston is positioned in the second direct acting valve. The second direct acting valve is fluidly connected to the first direct acting valve in a series configuration. The second control valve assembly is fluidly connected to the second valve chamber.

BACKGROUND

The present disclosure relates generally to pressure regulation systems,and more particularly to direct acting valves used in anti-icing systemsfor aircraft.

Operation of aircraft engines in adverse weather conditions or at highaltitudes can sometimes lead to ice forming on the exposed surfaces ofthe engine nacelle inlet. The build-up of ice on a nacelle surroundingthe engine limits the quantity of air being fed to the engine. Thisreduction in inlet airflow can result in a reduction of power output,efficiency and/or cooling capacity of the engine. Engine inletanti-icing systems commonly employ a thermal source, such as hot airbled from the engine core, which is applied to the nacelle inlet toprevent ice build-up on the external surfaces of the nacelle inlet.

Another concern with aircraft engines is the useful life of the aircraftengine and components. The build-up of ice near the inlet of the enginemay lead to large pieces of ice breaking loose from the inlet andflowing into the engine. Ice flowing into and through the engine maydamage components within the engine, such as airfoils, and componentsattached to the nacelle, such as inlet acoustic panels. The damagedcomponents may then require repair or replacement.

Current anti-icing systems include valves that do not compensate forincreases in air temperature with increasing bleed pressure and, as aresult, a delivered heat flux can result in damage to the nacelle fromoverheating.

SUMMARY

An anti-icing system of a nacelle inlet of an engine of an aircraftincludes a valve assembly fluidly connected to the nacelle inlet. Thevalve assembly includes first and second direct acting valves and firstand second control valve assemblies. The first direct acting valveincludes a first inlet, a first valve chamber fluidly connected to thefirst inlet, a first internal valve body circumferentially surroundingthe first valve chamber, a first outlet, and a first piston foradjusting a rate of flow of air through the first direct acting valve.The first piston is slidably engaged with the first internal valve body.The first control valve assembly is fluidly connected to the first valvechamber of the first direct acting valve. The second direct acting valveincludes a second inlet, a second valve chamber fluidly connected to thesecond inlet, a second internal valve body circumferentially surroundingthe second valve chamber, a second outlet, and a second piston foradjusting a rate of flow of air through the second direct acting valve.The second piston is slidably engaged with the second internal valvebody. The second direct acting valve is fluidly connected to the firstdirect acting valve in a series configuration such that the second inletof the second direct acting valve is directly connected to the firstoutlet of the first direct acting valve. The second control valveassembly is fluidly connected to the second valve chamber of the seconddirect acting valve.

A method of regulating air pressure in an anti-icing system of a nacelleinlet of an engine of an aircraft includes flowing air into a valveassembly. The valve assembly includes first and second direct actingvalves and first and second control valve assemblies. The first directacting valve includes a first valve chamber, a first internal valvebody, and a first piston slidably engaged with the first internal valvebody. The first control valve assembly is fluidly connected to the firstvalve chamber of the first direct acting valve. The second direct actingvalve includes a second valve chamber, a second internal valve body, anda second piston slidably engaged with the second internal valve body.The second direct acting valve is fluidly connected to the first directacting valve in a series configuration. The second control valveassembly is fluidly connected to the second valve chamber of the seconddirect acting valve. A heat flux of the nacelle inlet of the engine ofthe aircraft is controlled by the following steps. At least one of thefirst control valve assembly and the second control valve assembly areadjusted in response to the temperature of the air in the outlet of thesecond direct acting valve by controlling an amount of electricalcurrent fed into at least one of a first solenoid valve in the firstcontrol valve assembly and a second solenoid valve in the second controlvalve assembly. A rate of flow of air released into an ambientenvironment external to the valve assembly out of the at least one ofthe first control valve assembly and the second control valve assemblyis adjusted. At least one of the first direct acting valve and thesecond direct acting valve is moved by adjusting a pressure of air in atleast one of the first pressure chamber of the first direct acting valveand the second pressure chamber of the second direct acting valve. Arate of flow of the air out of the valve assembly is adjusted byadjusting a rate of flow of air past the at least one of the firstpiston and the second piston. A pressure of air flowing out of an outletof the second direct acting valve is controlled in response to theadjusted rate of flow of air out of the valve assembly. The air from theoutlet of the valve assembly is transported to the nacelle inlet of theengine of the aircraft.

A method of regulating air pressure in an anti-icing system of a nacelleinlet of an engine of an aircraft includes flowing air into a valveassembly. The valve assembly includes first and second direct actingvalves and first and second control valve assemblies. The first directacting valve includes a first valve chamber, a first internal valve bodysurrounding the first valve chamber, and a first piston slidably engagedwith the first internal valve body. The first control valve assembly isfluidly connected to a first valve chamber of the first direct actingvalve. The first control valve assembly includes a first solenoid with afirst ball element, a first plunger attached to the first ball element,and a first solenoid surrounding the first plunger, the first solenoidfor creating a magnetic field to interact with the first plunger. Thesecond direct acting valve is fluidly connected to the first directacting valve in a series configuration. The second direct acting valveincludes a second valve chamber, a second internal valve bodysurrounding the second valve chamber, and a second piston slidablyengaged with the second internal valve body. The second control valveassembly is fluidly connected to a second valve chamber of the seconddirect acting valve. The second control valve assembly includes a secondsolenoid with a second ball element, a second plunger attached to thesecond ball element, and a second solenoid surrounding the secondplunger, the second solenoid for creating a magnetic field to interactwith the second plunger. A heat flux of the nacelle inlet of the engineof the aircraft is controlled with the following steps. At least one ofa first solenoid valve in the first control valve assembly and a secondsolenoid valve in the second control valve assembly are energized byfeeding an electric current through the at least one of the firstsolenoid in the first control valve assembly and the second solenoid inthe second control valve assembly. A rate of flow of air released intoan ambient environment external to the valve assembly out of at leastone of the first control valve assembly and the second control valveassembly is increased by opening the at least one of the first solenoidvalve in the first control valve assembly and the second solenoid valvein the second control valve assembly in response to the electriccurrent. A pressure of air in at least one of a first pressure chamberof the first direct acting valve and a second pressure chamber of thesecond direct acting valve is decreased by decreasing a pressure of theair in the at least one of the first control valve assembly and thesecond control valve assembly in response to the increased rate of flowof air released into the ambient environment external to the valveassembly out of the at least one of the first control valve assembly andthe second control valve assembly. The at least one of the first pistonof the first direct acting valve and the second piston of the seconddirect acting valve are moved from an open position into a closedposition such that the closed position allows a lesser amount of air toflow past the at least one of the first piston and second piston thanthe open position by decreasing an effective area between the firstinternal valve body and the first piston or between the second internalvalve body and the second piston. A rate of flow of air past the atleast one of the first piston and the second piston is reduced inresponse to decreasing the effective area between the first internalvalve body and the first piston or between the second internal valvebody and the second piston. A pressure of air flowing out of an outletof the second direct acting valve is reduced in response to reducing therate of flow of air past the at least one of the first piston and thesecond piston. The air from the outlet of the valve assembly istransported to the nacelle inlet of the engine of the aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a gas turbine engine.

FIG. 2A is a cross-sectional view of a valve assembly with a first andsecond pressure valve and first and second control valves.

FIG. 2B is a cross-sectional view of the valve assembly with the firstand second pressure valve and first and second control valves shown ingreater detail.

FIG. 2C is a cross-sectional view of the valve assembly with a firstlocking mechanism in a locked position.

FIG. 3A is a partial cross-sectional view taken along 3-3 of FIG. 2B ofone embodiment of an interface between an internal valve body and apiston.

FIG. 3B is a partial cross-sectional view taken along 3-3 of FIG. 2Bshowing another embodiment of an interface between the internal valvebody and the piston.

FIG. 4 is a partial cross-sectional view taken along 4-4 of FIG. 2B of adirect acting valve including a valve lock mechanism.

FIG. 5 is a graph of valve assembly outlet pressure as a function ofvalve assembly inlet pressure.

FIG. 6 is a flowchart of a method of regulating air pressure in ananti-icing system of an aircraft.

FIG. 7 is a flowchart of another method of regulating air pressure in ananti-icing system of an aircraft.

DETAILED DESCRIPTION

The present disclosure describes non-limiting examples which provide asystem for maintaining the metal temperature of the nacelle inlet ashigher pressure and higher temperature air is supplied to the nacelleinlet, with the system including redundancy and a temperature probe forindicating over-temperature. The non-limiting examples discussed in thisdisclosure include controlling a pressure regulation set-point of avalve assembly such that when the pressure from the air to the valveassembly is high and associated temperature is hotter, control valveassemblies cause a reduction in a regulated output pressure, whichresults in maintaining an approximately fixed heat load to a nacelleinlet of an engine. First and second control valve assemblies, both withadjustable solenoid and pintle valves, can be adjusted and used torelease air into an ambient environment external to the control valveassemblies, thereby adjusting the pressure bias of first and seconddirect acting valves operating in series. Under normal operatingconditions, only the first direct acting valve is regulating while thesecond direct acting valve is fully open due to the second direct actingvalve's regulation pressure set-point being set higher than that of thefirst direct valve. The biased valve assembly allows the pressureset-point to be raised slightly higher when the pressure from the air tothe valve assembly is low and associated temperature is lower, to ensureany ice is fully melted and to not overheat the engine inlet when boththe pressure and temperature are higher.

FIG. 1 is a cross-sectional view of gas turbine engine 10, in atwo-spool turbofan configuration for use as a propulsion engine on anaircraft. As shown in the figure, low spool 12 includes low pressurecompressor (“LPC”) 14 and low pressure turbine (“LPT”) 16, rotationallycoupled via low pressure shaft 18. High spool 20 includes high pressurecompressor (“HPC”) 22 and high pressure turbine (“HPT”) 24, rotationallycoupled via high pressure shaft 26. High spool 20 is coaxially orientedabout low spool 12, along engine centerline (or turbine axis) C_(L),with combustor 28 positioned in flow series between high pressurecompressor 22 and high pressure turbine 24.

Nacelle 30 is oriented about the forward end of gas turbine engine 10.Fan casing 32 extends along on the radially inner surface of nacelle 30,from propulsion fan 34 to fan exit guide vane 36. Propulsion fan 34 isrotationally coupled to low spool 12 via fan shaft 38, generatingpropulsive flow F_(P) through fan duct (or bypass duct) 40. In advancedengine designs, fan drive gear system 42 couples fan shaft 38 to lowspool 12 at low pressure shaft 18, providing independent fan speedcontrol for reduced noise, emissions, and improved operating efficiency.

Nacelle 30 extends forward of the gas turbine engine 10 and definesinlet 44 for incoming fluid. Nacelle 30 includes inner barrel 46, outerbarrel 48, bulkhead 50, and inlet shell 52. Inner barrel 46 definesradially outer flow surface 54 for a portion of the flowpath of gasturbine engine 10. Outer barrel 48 defines outer flow surface 56 for theexternal medium flowing about gas turbine engine 10. A radial separationbetween inner barrel 46 and outer barrel 48 defines annular chamber 58there between. Inlet shell 52 is the leading edge for nacelle 30. Inletshell 52 and bulkhead 50 bound annular shell cavity 60.

Fluid pressure regulation system 62 is fluidly connected to HPC 22 andextends into annular chamber 58. Anti-icing system 64 is positionedwithin nacelle 30 and transfers fluid, in this example air, into annularshell cavity 60. Fluid pressure regulation system 62 includes valveassembly 66 which can be made up of one or more of a variety of valvesand flow regulators to control the flow of air through fluid pressureregulation system 62 (as will be discussed with respect to the remainingfigures). In other non-limiting embodiments, fluid pressure regulationsystem 62 can extend along the interior of annular chamber 58 beforeintroducing air into annular shell cavity 60.

FIG. 2A is a cross-sectional view of valve assembly 100, which can beused as or with valve assembly 66 in FIG. 1. The major components ofvalve assembly 100 include first direct acting valve 102A, first controlvalve assembly 104A, second direct acting valve 102B, and second controlvalve assembly 104B. First direct acting valve 102A and second directacting valve 102B include non-limiting examples of direct acting valvesthat regulate outlet pressure exiting from valve assembly 100.

First direct acting valve 102A is fluidly connected to second directacting valve 102B in a series configuration. First control valveassembly 104A is fluidly connected to first direct acting valve 102A andsecond control valve assembly 104B is fluidly connected to second directacting valve 102B.

Direct acting valves are characterized in their capability of theregulating piston to react immediately to fluctuations of inlet pressureas compared to other types of valves, such as servo-regulated valveswhich sense downstream pressure and then move an upstream valve.Non-direct acting valves typically include delays and/or time-lagbetween the time a valve controller reacts to downstream pressure and aservo-piston adjusts to in order to regulate outlet pressure.

Valve assembly 100 is an example of two direct acting valves in a seriesconfiguration with corresponding controllers to adjust servo pressuresto modulate regulating valves and control regulated pressure. Valveassembly 100 includes two of the same, direct acting type pressureregulating valves in series, with first direct acting valve 102A actingas the primary pressure regulator under normal operating conditions andsecond direct acting valve 102B acting as a backup in case of a failureof the primary. Normally, because a set-point of second direct actingvalve 102B is set higher than a set-point of first direct acting valve102A, second direct acting valve 102B remains fully open while firstdirect acting valve 102A regulates downstream pressure. In the event ofa failure condition, first direct acting valve 102A would be locked openand second direct acting valve 102B would provide pressure regulated airto the cowl. Utilizing a direct acting valve rather than a servoactuated valve reduces pressure overshoots for rapid inlet pressuretransients. Valve assembly 100 uses two of the same direct acting valveswith different set points which adds cost reduction and simplicity.

FIG. 2B is a cross-sectional view of valve assembly 100 from FIG. 2Ashown in greater detail. Valve assembly 100 includes first direct actingvalve 102A, first control valve assembly 104A, second direct actingvalve 102B, second control valve assembly 104B, and full authoritydigital engine control (“FADEC”) 106 of the aircraft or some othersource to open or shut first direct acting valve 102A and second directacting valve 102B either individually or simultaneously.

First direct acting valve 102A includes first inlet 108A, first outlet110A, first internal valve body 112A, first valve chamber 114A, firstouter flow chamber 116A, first piston 118A, first lip element 120A,first lock mechanism 122A, first upstream wall 124A, first hole 126A,and first orifice plug 128A. First direct acting valve 102A and seconddirect acting valve 102B include non-limiting examples of direct actingvalves that regulate outlet pressure exiting from valve assembly 100.

First inlet 108A is an orifice in first direct acting valve 102A. Firstinlet 108A is fluidly connected to HPC 22 through fluid regulationsystem 62 (as seen in FIG. 1). First inlet 108A provides an openingthrough which flow W_(I) of air from fluid regulation system 62 (fromFIG. 1) enters into first direct acting valve 102A. First outlet 110A isan orifice in first direct acting valve 102A. First outlet 110A providesan opening through which partially regulated flow W_(PR) of air istransferred from first direct acting valve 102A to second direct actingvalve 102B.

First valve chamber 114A is positioned within first direct acting valve102A. First valve chamber 114A is bounded in an upstream direction byfirst upstream wall 124A, in a downstream direction by first piston118A, and in a radial direction by first internal valve body 112A offirst direct acting valve 102A. First valve chamber 114A is fluidlyconnected to first inlet 108A by first hole 126A in first upstream wall124A.

First piston 118A is a pressure regulating element positioned withinfirst direct acting valve 102A. First piston 118A is slidably engagedwith first internal valve body 112A of first direct acting valve 102Asuch that first piston 118A is capable of translating linearly withinfirst direct acting valve 102A from a fully open position to a fullyclosed position. For example, in FIG. 2B first piston 118A is shown in apartially open position. First piston 118A includes first lip element120A. First lip element 120A is located on an upstream end of firstpiston 118A and extends outwardly in a generally radial direction fromfirst piston 118A. First lip element 120A can be monolithically formedwith or connected to first piston 118A, and in other non-limitingembodiments first lip element 120A can be attached to first piston 118Athrough physical or chemical attachment means. First throat 130A extendsbetween first internal valve body 112A and first lip element 120Aforming a passage from first outer flow chamber 116A to first outlet110A. A distance of first throat 130A determines an effective area offlow through first throat 130A by forming a circumferential or annulargap between first internal valve body 112A and first lip element 120Athrough which flow W_(I) of air transfers from first outer flow chamber116A to first outlet 110A.

Valve assembly 100 also includes first lock mechanism 122A positioned infirst valve chamber 114A of first direct acting valve 102A. First lockmechanism 122A is rotatably connected to first direct acting valve 102A.In FIG. 2B, first locking mechanism 122A is shown in an un-lockedposition.

First direct acting valve 102A also includes first hole 126A positionedon first upstream wall 124A of first valve chamber 114A. In onenon-limiting example, the diameter of first hole 126A can include adiameter of approximately 0.020 to 0.030 inches (0.051 to 0.0762centimeters). First hole 126A fluidly connects first inlet 108A withfirst valve chamber 114A. In valve assembly 100, flow W_(I) of air fromfluid regulation system 62 flows into first valve chamber 114A throughfirst hole 126A and directly adjusts the pressure within first valvechamber 114A.

In FIG. 2B, valve assembly 100 is shown with first orifice plug 128Apositioned in first hole 126A. First orifice plug 128A is removablypositioned in first hole 126A in upstream wall 142A of first valvechamber 114A. First orifice plug 128A includes a passage and providescontamination resistance of flow W_(I) of air from fluid regulationsystem 62 as flow W_(I) of air enters into first valve chamber 114A byforcing flow W_(I) of air to turn into first orifice plug 128A, throughfirst orifice plug 128A, and into first valve chamber 114A.

First direct acting valve 102A is configured such that first piston 118Amoves along a linear pathway in response the change in pressure in firstvalve chamber 114A due to a change in flow W_(I) of air from fluidregulation system 62 entering into first valve chamber 114A throughfirst hole 126A. In some non-limiting embodiments, the term move issynonymous with translate, actuate, slide, adjust, modulate, changeposition, and other terms relating to lateral positional adjustment. Thepositioning of first piston 118A regulates an amount of partiallyregulated flow W_(PR) of air flowing from first outlet 110A to seconddirect acting valve 102B by controlling an effective area that flowW_(I) of air passes through as flow W_(I) of air travels through firstdirect acting valve 102A, past first lip element 120A of first piston118A, and through first outlet 110A.

First lip element 120A experiences closing force F_(LIP) on first lipelement 120A as a function of inlet pressure. There is a static pressuredistribution on first piston 118A due to closing force F_(LIP) on firstlip element 120A in an upstream direction (to the left in FIG. 2B) andbias force F_(REF) acting on first piston 118A in a downstream direction(to the right in FIG. 2B). As will be discussed further in FIGS. 3A-3B,the static pressure distribution is a function of the lip geometry offirst lip element 120A and can be altered by changing the geometry(e.g., angle) of first lip element 120A.

Under normal operating conditions, first lock mechanism 122A occupies anun-locked position (shown in FIG. 2B) such that first piston 118A isallowed to travel or move between a fully open position and a fullyclosed position. First lock mechanism does not block or impede movementof first piston 118A when first lock mechanism 122A occupies theun-locked position. In an event of a failure of first control valveassembly 104A, first lock mechanism 122A can be toggled into a lockedposition which locks first piston 118A into a fully open position (tothe right of FIG. 2B). See FIGS. 2C and 4 for additional discussion offirst locking mechanism 122A.

First control assembly 104A includes first solenoid valve 132A and firstpintle valve 134A. First solenoid valve 132A includes first solenoid136A, first ball element 138A, first plunger 140A, first solenoid spring142A, and first solenoid seat 144A.

First solenoid valve 132A includes an electrically controllable releasevalve for releasing air from first valve chamber 114A into an ambientenvironment external to valve assembly 100. First solenoid 136A includesa solenoid for producing a magnetic field upon the application ofelectric current to first solenoid 136A. First ball element 138Aincludes a valve element for controlling an effective area of flowthrough which air can flow past first ball element 138A, out of firstsolenoid valve 132A, and into the ambient environment external to valveassembly 100. First ball element 138A is attached to or is in contactwith first plunger 140A. First plunger 140A includes magnetic materialfor interacting with the magnetic field produced by first solenoid 136A.In a non-limiting example, first ball element 138A and first plunger140A can be formed from a single piece of material, or alternatively canbe connected through physical or chemical attachment means. Firstsolenoid spring 142A includes first spring 142A for biasing firstplunger 140A to the left in FIG. 2B, by pushing against first plunger140A. First solenoid seat 144A includes an annular sealing element forsealing engagement with first ball element 138A.

First pintle valve 134A includes first pintle 146A, first pintle spring148A, first pintle housing 150A, first threadably adjustable biasingelement 152A, and first pintle seat 154A.

First pintle valve 134A provides a non-limiting adjustable release valvefor releasing air from first valve chamber 114A into an ambientenvironment external to valve assembly 100. First pintle 146A of firstpintle valve 134A includes a conical shaped element that is slidablyengaged with first pintle housing 150A. In other non-limitingembodiments, first pintle valve 134A can include non-conicalconfigurations such as a simple ball. First pintle spring 148A includesa spring element for biasing first pintle 146A to the right in FIG. 2B,by pushing against first pintle 132 and first threadably adjustablebiasing element 152A. First threadably adjustable biasing element 152Aincludes a threadably adjustable element for threadably adjusting thetension, or spring-force, in first pintle spring 148A. First pintle seat154A includes an annular sealing element for sealing engagement withfirst pintle 146A.

First valve chamber 114A is fluidly connected to first control assembly104A. First solenoid valve 132A and first pintle valve 134A are fluidlyconnected to first valve chamber 114A by first line 156A. First solenoidvalve 132A and first pintle valve 134A are also fluidly connected toeach other by first line 156A. First solenoid valve 132A and firstpintle valve 134A function either separately or in tandem to control theamount of air released into the ambient environment external to valveassembly 100 thereby controlling amount of P_(REF) within first valvechamber 114A.

FADEC 106 includes a system for controlling electrical systems withinthe aircraft relating to performance aspects of aircraft. First controlvalve assembly 104A and second control valve assembly 104B areelectrically connected to FADEC 106 by first wires 158A and second wires158B respectively. First solenoid valve 132A can be electricallyconnected by first wires 158A to FADEC 106. Second solenoid valve 132Bcan be electrically connected by second wires 158B to FADEC 106.

First solenoid valve 132A can receive an electrical signal from FADEC106 which controls first solenoid valve 132A and a position of firstball element 138A. As the electrical signal is received by, or fed into,first solenoid valve 132A, first solenoid 136A becomes energizedcreating a magnetic field which is applied to first plunger 140A causingfirst ball element 138A to actuate along a linear pathway and into anenergized position. The electrical signal can be terminated tode-energize first solenoid 136A thereby reducing the magnetic fieldwhich causes first plunger 140A with first ball element 138A to actuatelinearly into a de-energized position. First solenoid valve 132A can bein a default closed position, such that first ball element 138A occupiesa closed positioned when first solenoid 136A is de-energized. Firstsolenoid valve 132A includes a default closed position due to firstsolenoid spring 142A biasing first plunger 140A to the left in FIG. 2Bso that a distal (left most) end of first plunger 140A pushes first ballelement 138A against first solenoid seat 144A creating a seal preventingair from passing first ball element 138A.

Upon being energized, a magnetic field of first solenoid 136A drawsfirst plunger 140A with first ball element 138A towards first solenoidspring 142A, thereby compressing first solenoid spring 142A, drawingfirst ball element 138A away from first solenoid seat 144A, and openingfirst solenoid valve 132A. In another non-limiting embodiment, firstplunger 140A can move out of the way and air can push first ball element138A away from first solenoid seat 144A. In other non-limitingembodiments, first solenoid valve 132A can receive electrical signalsfrom pilot instrumentation or other various electronic controls oravionic systems of the aircraft.

In another non-limiting embodiment, first solenoid valve 132A can alsoinclude a default open configuration such that first ball element 138Aoccupies an open position (e.g., separated from first solenoid seat144A) when de-energized and a closed position upon receiving anelectrical signal and becoming energized. In FIG. 2B, first ball element138A is shown in a closed position to the left of first solenoid valve132A (and to the left in FIG. 2B), which can be either an energized orde-energized position. First solenoid valve 132A can receive theelectrical signal from FADEC 106 and/or from other electronic devices inthe aircraft such as pilot instrumentation or aircraft avionics.

In response to a change in pressure in first line 156A, first pintle146A of first pintle valve 134A moves in a linear motion within firstpintle housing 150A thereby causing first pintle 146A to actuate. Asfirst pintle 146A actuates, an effective vent area of first pintle valve134A is varied thereby releasing adjusted amounts of air out of firstpintle valve 134A and into an ambient environment external to valveassembly 100 from first control valve assembly 104A. First pintle spring148A biases first pintle 146A into a more closed position towards firstpintle seat 154A (to the right in FIG. 2B). The position of first pintle146A determines the amount of fluid allowed to pass out of first pintlevalve 134A and into ambient thereby setting a resultant pressure infirst valve chamber 114A of first direct acting valve 102A. For example,when first pintle 146A is positioned to the right in FIG. 2B, lessventing of fluid flow from valve assembly 100 would occur therebyincreasing the pressure in first valve chamber 114A and causing firstpiston 118A to move into a more open position. Alternatively, when firstpintle 146A is positioned to the left in FIG. 2B (as shown in FIG. 2B)more venting of air out of valve assembly 100 from first control valveassembly 104A would occur thereby decreasing the pressure in first valvechamber 114A and causing first piston 118A to move to the left of FIG.2B into a more closed position.

During operation of valve assembly 100, first control valve assembly104A effectively controls the amount of pressure received by first valvechamber 114A. As first solenoid valve 132A and first pintle valve 134Aare opened, an amount of air allowed to pass through first solenoidvalve 132A and first pintle valve 134A into an ambient environmentexternal to valve assembly 100 is increased. As the amount of airexiting first control valve assembly 104A increases, the resultingpressure within first valve chamber 114A decreases causing first piston118A to move to the left of FIG. 2B in response the decrease in pressurein first valve chamber 114A. As first piston 118A moves to the left ofFIG. 2B, an effective area of flow through first direct acting valve102A is decreased therefore decreasing the amount of partially regulatedflow W_(PR) of air exiting from first outlet 110A.

As first solenoid valve 132A and first pintle valve 134A are closed, anamount of air allowed to pass through first solenoid valve 132A and intoan ambient environment external to valve assembly 100 is decreased. Asthe amount of air exiting first control valve assembly 104A decreases,the resulting pressure within first valve chamber 114A increases causingfirst piston 118A to move to the right of FIG. 2B in response theincrease in pressure in first valve chamber 114A. As first piston 118Amoves to the right of FIG. 2B, an effective area of flow through firstdirect acting valve 102A is increased therefore increasing the amount ofpartially regulated flow W_(PR) of air exiting from first outlet 110A.

Second direct acting valve 102B includes second inlet 108B, secondoutlet 110B, second internal valve body 112B, second valve chamber 114B,second outer flow chamber 116B, second piston 118B, second lip element120B, second lock mechanism 122B, second upstream wall 124B, second hole126B, second orifice plug 128B, and temperature probe 160. Secondcontrol valve assembly 104B includes second solenoid valve 132B andsecond pintle valve 134B. Second solenoid valve 132B includes secondsolenoid 136B, second ball element 138B, second plunger 140B, secondsolenoid spring 142B, and second solenoid seat 144B. Second pintle valve134B includes second pintle 146B, second pintle spring 148B, secondpintle housing 150B, second threadably adjustable biasing element 152B,and second pintle seat 154B.

Throughout FIG. 2B, elements corresponding to first direct acting valve102A and first control valve assembly 104A are discussed with characterreference elements that include the letter “A,” while analogous elementscorresponding to second direct acting valve 102B and second controlvalve assembly 104B are discussed with character reference elementsincluding the letter “B.” As such, the discussion of the elements offirst direct acting valve 102A and first control valve assembly 104Adiscussed below also extends to describe the analogous elements ofsecond direct acting valve 102B and second control valve assembly 104B.Second direct acting valve 102B and second control valve assembly 104Binclude all of the same elements as first direct acting valve 102A andfirst control valve assembly 104A. In other non-limiting embodiments,first control valve assembly 104A and second control valve assembly 104Bdo not include first solenoid valve 132A or second solenoid valve 132B.

Second piston 112B of second direct acting valve 102B occupies a fullyopen position in FIG. 2B (to the right in FIG. 2B).

In addition to the similar elements of first direct acting valve 102A,second direct acting valve 102B also includes temperature probe 160.Temperature probe 160 includes a probe for measuring temperature.Temperature probe 160 extends into second outlet 108B and into aflowpath of flow W_(O) of air exiting valve assembly 100 out of secondoutlet 108B. Temperature probe 160 measures a temperature of flow W_(O)of air. Temperature probe 160 is electrically connected to FADEC 106 bywires 162. In other non-limiting embodiments, temperature probe 160 canbe electrically connected to other control elements or electronicdevices of the aircraft such as pilot instrumentation or other aircraftavionics. Temperature probe 160 can alternatively be a temperatureswitch that is wired to relays in order to close both first directacting valve 102A and second direct acting valve 102B withoutintervention by FADEC 106. In other non-limiting embodiments,temperature probe 160 can be located in adjacent downstream ducts.

Upon measuring the temperature of flow W_(O) of air that is above adesignated threshold temperature, a signal from temperature probe 160can cause first solenoid valve 132A and second solenoid valve 132B to beenergized thereby partially or fully closing first direct acting valve102A and second direct acting valve 102B and reducing or stopping flowW_(O) of air out of second outlet 108B. First solenoid valve 132A andsecond solenoid valve 132B can remain energized until the temperature offlow W_(O) of air decreases below the designated threshold temperatureand first solenoid valve 132A and second solenoid valve 132B arede-energized restoring regulation of flow W_(O) of air. A cycling timeof temperature probe 160 is a function of a hysteresis of temperatureprobe 160 and a time constant, and the function can be optimized forsystem operation. The ability to send a signal to first control valveassembly 104A and second control valve assembly 104B is necessary if,for example, first direct acting valve 102A was locked open due to afailure condition. Temperature probe 160 provides additional preventionof the temperature of nacelle 30 exceeding too high a temperature bymonitoring the temperature of flow W_(O) of air that is delivered toinlet 44 of nacelle 30 via anti-icing system 64.

First outlet 110A of first direct acting valve 102A is directlyconnected to second inlet 108B of second direct acting valve 102Bforming intermediate flow chamber 164 between first outlet 110A andsecond inlet 108B. As flow W_(I) of air enters into first direct actingvalve 102A through first inlet 108A, a portion of flow W_(I) of airenters into first valve chamber 114A through first orifice plug 128A infirst hole 126A, and another portion of flow W_(I) of air is divertedinto first outer flow chamber 116A. As flow W_(I) of air enters intofirst valve chamber 114A through first orifice plug 128A in first hole126A, reference pressure P_(REF) within first valve chamber 114Aincreases. As flow W_(I) of air flows into and through first outer flowchamber 116A, flow W_(I) of air flows through first throat 130A betweenfirst internal valve body 112A and first lip element 120A, past firstlip element 120A of first piston 118A, and into intermediate flowchamber 164 formed between first outlet 110A and second inlet 108B. Asflow W_(I) of air flows past first lip element 120A of first piston118A, flow W_(I) of air is regulated becoming partially regulated flowW_(PR) of air. As partially regulated flow W_(PR) of air changes withinintermediate flow chamber 164, regulated pressure P_(REG) of flow W_(PR)of air within intermediate flow chamber 164 also changes. In FIG. 2B,because second direct acting valve 102B is in a fully open position,regulated pressure P_(REG) of flow W_(PR) of air within intermediateflow chamber 164 also represents the resultant regulated pressureP_(REG) of flow W_(O) of air out of second outlet 108B due to flowW_(PR) of air passing unrestricted past second lip element 114B and intosecond outlet 108B.

The resultant regulated pressure P_(REG) of flow W_(O) of air out ofsecond outlet 108B can be represented by the following equation:

$\begin{matrix}{P_{REG} = {P_{REF} - \frac{F_{LIP}}{A}}} & (1)\end{matrix}$

Where: reference pressure P_(REF) is a reference pressure inside firstvalve chamber 114A, closing force F_(LIP) is a closing force acting onfirst lip element 120A in an up-stream direction (to the left in FIG.2B), and A is an area of first outlet 110A (and of intermediate flowchamber 164). Closing force F_(LIP) can be represented by the followingequation:F _(REG) =F _(REF) −F _(LIP)  (2)

Bias force F_(REF) is an inlet reference bias force acting on firstpiston 118A in a downstream direction (to the right in FIG. 2B) fromwithin first valve chamber 114A due to P_(REF) being applied to firstpiston 118A. Bias force F_(REG) is an outlet regulated bias force actingon first piston 118A in an up-stream direction (to the left in FIG. 2B)from within first outlet 110A due to P_(REG) being applied to firstpiston 118A.

As can be seen with equation (1), the amount of bias of regulatedpressure P_(REG) can be adjusted by varying the area of first outlet110A, closing force F_(LIP) acting on first lip element 120A, andreference pressure P_(REF) inside first valve chamber 114A. As can beseen with equation (2), as closing force F_(LIP) increases and biasforce F_(REF) remains constant, bias force F_(REG) and regulatedpressure P_(REG) decrease. In the instance of pressure P_(in) of flowW_(I) starting with a pressure below a set-point of regulated pressureP_(REG), first direct acting valve 102A is fully open and there is noclosing force F_(LIP). As pressure P_(in) of flow W_(I) increases,regulated pressure P_(REG) would start to increase thereby causing firstpiston 118A to move toward a closed position in order to maintainregulated pressure P_(REG) at a constant pressure. The movement of firstpiston 118A towards a more closed position results in an increase ofclosing force F_(LIP) thereby causing regulated pressure P_(REG) to bereduced in order to maintain a force balance applied to first lipelement 120A. Closing force F_(LIP) can be used to reduce regulatedpressure P_(REG), and thereby flow W_(O) of air, as a function of inletpressure so as to prevent overheating of inlet 44 of nacelle 33.

As pressure P_(in) of flow W_(I) increases, regulated bias force F_(REG)on first piston 118A increases which causes first piston 118A to move tothe left of FIG. 2B. As first piston 118A moves to the left of FIG. 2B,a distance of first throat 130A between first internal valve body 112Aand first lip element 120A decreases. As a distance of first throat 130Adecreases, an effective area that flow W_(I) of air passes through alsodecreases as air travels through first outer flow chamber 116A, pastfirst piston 118A, and into first outlet 110A. Conversely, as P_(REG)decreases, regulated bias force F_(REG) on first piston 118A decreaseswhich causes first piston 118A to move to the right of FIG. 2B thereforeincreasing the effective area that flow W_(I) of air passes through asit travels through first outer flow chamber 116A, past first piston118A, and into first outlet 110A.

Flow W_(O) of air is transferred out of second outlet 108B from valveassembly 100 to nacelle 30 of FIG. 1, which includes anti-icing system64, of gas turbine engine 10. Thermal energy is then transferred fromflow W_(O) of air to nacelle 30 through anti-icing system 64 and thebuild-up of ice on nacelle 30, and in particular on a leading edge ofinlet 44, is reduced in response to transferring thermal energy fromflow W_(O) of air to nacelle 30 and into annular shell cavity 60. Forexample, lower pressure P_(o) of flow W_(O) of air exiting out of secondoutlet 108B results in less flow W_(O) of air to anti-icing system 64and a resulting lower heat flux to nacelle 30 and thereby reducing metaltemperature of inlet 44 of nacelle 30. In another example, higherpressure P_(o) of flow W_(O) of air exiting out of second outlet 108Bresults in a higher flow W_(O) of air to anti-icing system 64 and aresulting in a higher metal temperature of inlet 44 of nacelle 30.

By changing the geometry of first and second lip elements 114A and 114B,a change in regulated pressure P_(o) of flow W_(O) of air as a functionof pressure P_(in) on flow W_(I) of air from fluid regulation system 62can be altered to optimize system performance. Additionally, the use ofvalve assembly 100 with two direct acting pressure regulating valves inseries minimizes overshoots in pressure P_(o) of flow W_(O) of air ascompared to servo actuated valves. The use of valve assembly 100 withtemperature probe 160 provides additional safety features to preventoverheating inlet 44 of nacelle 30 by commanding both first directacting valve 102A and second direct acting valve 102B closed.

FIG. 2C is a cross-sectional view of valve assembly 100 with firstlocking mechanism 122A in a locked position.

First locking mechanism 122A is shown in FIG. 2C as occupying a lockedposition in which first locking mechanism 122A is rotated approximately90° from a position of first locking mechanism 122A shown in FIG. 2B.First locking mechanism 122A occupies a locking position due to firstlocking mechanism 122A being rotated to come into contact with firstpiston 118A thereby preventing first piston 118A from moving out of afully open position.

Valve assembly 100 of FIG. 2C is an example of two direct acting valvesin a series configuration with corresponding controllers to adjust servopressures to modulate regulating valves and control regulated pressure.The system consists of, two of the same, direct acting type pressureregulating valves in series. In FIG. 2C first direct acting valve 102Ais locked open by first locking mechanism 122A while second directacting valve 102B is acting as the primary pressure regulating valve.With first direct acting valve 102A being locked in a fully open state,second direct acting valve 102B regulates pressure P_(o) of flow W_(O)of air. In one non-limiting embodiment, FIG. 2C can represent a failurecondition of first control valve assembly 104A resulting in first directacting valve 102A being locked open and second direct acting valve 102Aregulating pressure P_(o) of flow W_(O) of air to anti-icing system 64.

In the instance of a failure of first control valve assembly 104A,second direct acting valve 102B and second control valve assembly 104Bregulate flow W_(O) of air from valve assembly 100. Using second valveassembly 104B to regulate flow W_(O) of air from valve assembly 100differs from normal operating conditions because under normal operatingconditions, a regulation set-point of second direct acting valve 102Band second control valve assembly 104B is set higher than a regulationset-point of first direct acting valve 102A and first control valveassembly 104A. The higher regulation set-point of second direct actingvalve 102B and second control valve assembly 104B results in seconddirect acting valve 102B remaining open under normal operatingconditions while first direct acting valve 102A and first controlassembly 104A regulate pressure P_(REG) of flow W_(PR) and resultingregulated pressure P_(REG) of flow W_(O). In some non-limitingembodiments, second pintle spring 148B can include a different springforce than first pintle spring 148A in order to cause regulationset-point of second direct acting valve 102B to be higher than theset-point

In another non-limiting embodiment, both first locking mechanism 122Aand second locking mechanism 116B can occupy a locked open position toprevent both first piston 118A and second piston 112B respectively frommoving thereby locking first and second direct acting valves 102A and102B in an open position allowing the pressure of flow W_(O) of air tobe unregulated.

FIG. 3A is a partial cross-sectional view taken along 3-3 in FIG. 2B ofa first interface between first internal valve body 112A and first lipelement 120A of first piston 118A. FIG. 3A includes first piston 118A,first lip element 120A, first internal valve body 112A, first axial face166A of first lip element 120A, plane P_(i), first axial face 168A offirst internal valve body 112A, plane P_(ii), and first throat 130A.First lip element 120A includes first axial face 166A. First internalvalve body 112A includes first axial face 168A. First axial face 166Aextends at angle θ_(LIP) between plane P_(i) extending in an axialdirection and first axial face 166A. First axial face 168 of firstinternal valve body 112A extends at angle θ_(VB) between plane P_(i)extending in an axial direction and first axial face 168A. In onenon-limiting embodiment, expansion angle θ_(EXP), equivalent to thedifference between angle θ_(LIP) and angle θ_(VB), includes an anglefrom 15° to 60°. In FIG. 3A, angle θ_(LIP) between plane P_(i) extendingin an axial direction and first axial face 166A includes an angle ofapproximately 60°, angle θ_(VB) between plane P_(i) extending in anaxial direction and first axial face 168A includes an angle ofapproximately 45°, and expansion angle θ_(EXP) includes an angle of 15°.In other non-limiting examples, a distance of first throat 130A variesbased on angles θ_(LIP) and θ_(VB). First throat 130A represents adistance between first axial face 166A of first lip element 120A andfirst axial face 168A of first internal valve body 112A.

As discussed above with reference to first lip element 120A in FIG. 2B,the amount of closing force F_(LIP) acting on first lip element 120A canbe adjusted by varying reference bias force F_(REF) and regulated biasforce F_(REG) acting on first piston 118A. The distance of first throat130A affects an effective area that flow W_(I) of air passes through asflow W_(I) of air travels past first lip element 120A and first internalvalve body 112A which affects regulated bias force F_(REG) acting onfirst piston 118A.

Expansion angle θ_(EXP) determines the pressure distribution downstreamof first throat 130A. With a smaller expansion angle θ_(EXP), a drop inpressure across first throat 130A is not as great as the drop inpressure across first throat 130A compared to a larger expansion angleθ_(EXP). With a smaller drop in pressure across first throat 130A, a netforce on first lip element 120A is less, causing a decrease in areduction in regulated pressure P_(REG) as the pressure of flow W_(I)increases. A larger expansion angle θ_(EXP) results in a more rapid dropin pressure across first throat 130A, causing an increase in the netforce on first lip element 120A, and resulting in an increased drop inregulated pressure P_(REG) as the pressure of flow W_(I) increases.

In one non-limiting example, as the distance of first throat 130Aincreases, the effective area that flow W_(I) passes through as flowW_(I) of air travels past first lip element 120A and first internalvalve body 112A increases allowing a higher rate of flow W_(I) of airpast first lip element 120A and first internal valve body 112A. Thehigher rate of flow W_(I) of air past first lip element 120A and firstinternal valve body 112A causes an increase in P_(REG) which results inan increase in F_(REG). The increase in F_(REG) results from a decreasein F_(LIP) in accordance with equation (2) (taking into account a staticF_(REF) for the purpose of the example). The decrease in F_(LIP) resultsin an increase in P_(REG) in accordance with equation (1), and aresulting higher pressure set-point of the corresponding valve assembly,such as valve assembly 100 (as seen in FIG. 5).

In another non-limiting example, as the distance of first throat 130Adecreases, the effective area that flow W_(I) of air passes through asflow W_(I) of air travels past first lip element 120A and first internalvalve body 112A decreases allowing a lower rate of flow W_(I) of airpast first lip element 120A and first internal valve body 112A. Thelower rate of flow W_(I) of air past first lip element 120A and firstinternal valve body 112A causes a decrease in P_(REG) which results in adecrease in F_(REG). The decrease in F_(REG) results from an increase inF_(LIP) in accordance with equation (2) (taking into account a staticF_(REF) for the purpose of the example). The increase in F_(LIP) resultsin a decrease in P_(REG) in accordance with equation (1), and aresulting lower pressure set-point of the corresponding valve assembly,such as valve assembly 100 (as seen in FIG. 5).

FIG. 3B is a partial cross-sectional view of a second interface betweenfirst internal valve body 112A and first lip element 120A′ of firstpiston 118A. First lip element 120A′ includes first axial face 166A′.First internal valve body 112A includes first axial face 168A′. Firstthroat 130A′ represents a distance between first axial face 166A′ offirst lip element 120A and first axial face 168A′ of first internalvalve body 112A. First axial face 166A extends at angle θ_(LIP)′ betweenplane P_(i) extending in an axial direction and first axial face 166A.First axial face 168 of first internal valve body 112A extends at angleθ_(VB)′ between plane P_(i) extending in an axial direction and firstaxial face 168A. In one non-limiting embodiment, expansion angleθ_(EXP)′, which equivalent to the difference between angle θ_(LIP)′ andangle θ_(VB)′, includes an angle from 15° to 60°. In FIG. 3B, angleθ_(LIP)′ between plane P_(i) extending in an axial direction and firstaxial face 166A includes an angle of approximately 105°, angle θ_(VB)′between plane P_(i) extending in an axial direction and first axial face168A includes an angle of approximately 45°, and expansion angleθ_(EXP)′ includes an angle of 60°.

FIG. 4 is a cross-sectional view taken along 4-4 in FIG. 2B of firstlock mechanism 122A positioned in first direct acting valve 102A. Firstlock mechanism 122A includes first actuation bolt 170A, first lock bolt172A, and first lock arm 174.

First actuation bolt 170A extends into first direct acting valve 102A,through first outer flow chamber 116A, through first internal valve body112A, and into valve chamber 110A of direct acting valve 102A. Firstlock arm 174A is attached to first actuation bolt 170A such that asfirst actuation bolt 170A is rotationally engaged from outside of directacting valve 102A, first lock arm 174A pivots to extend towards firstpiston 118A (not shown in FIG. 4) to hold first piston 118A in a fullyopen position and prevent first piston 118A from moving (as shown inFIG. 2C). First lock mechanism 122A is shown to include first lock bolt172A, which engages with first lock mechanism 122A to hold firstactuation bolt 170A in a rotated position thereby holding first lock arm174A in a rotated position preventing first piston 118A from moving.Upon removing first lock bolt 172A from first locking mechanism 122A,first actuation bolt 170A can be freely rotated to adjust first lock arm174A into an original un-rotated position thereby allowing first piston118A to freely move within first direct acting valve 102A.

FIG. 5 shows graph 500 of valve outlet pressure as a function of valveinlet pressure of valve assembly 100 shown in FIG. 2B. During engineoperation, as the engine air pressure and temperature increases, valveoutlet pressure increases until the valve inlet pressure achieves setpoint A.

In a system without a lip bias force with direct acting valves in aseries configuration, such as valve assembly 100 for example, furtherincreases to the valve inlet pressure result in a constant outletpressure P₁ as indicated by the zero slope of the line between set-pointA and set-point B. Without a reduction in valve outlet pressure P₁, thecorresponding nacelle inlet temperature continues to increase as thevalve inlet pressure is increased between set-point A and set-point Bpotentially causing damage to the nacelle of a gas turbine engine.

In a system with a valve assembly including direct acting valves in aseries configuration, such as valve assembly 100 for example, onceregulated pressures P₃ and P₂ reach set-points C and D respectively,further increases to the valve inlet pressure result in reducedregulated pressures P₃ and P₂ as indicated by the generally negativeslopes of lines P₃ and P₂ between set-point A and set-point B. With areduction in regulated pressure P_(REG), causing a decrease in flow andreduced heat flux to the nacelle, the corresponding nacelle surfaceinlet temperature is maintained at a safe value as the valve inletpressure is increased between set-point A and set-point B.

Valve assembly outlet pressure P₃ represents a regulated outlet pressureof a valve assembly with the first direct acting valve in a modulatingstate and the second direct acting valve in a fully open un-modulatingstate. Valve assembly outlet pressure P₂ represents a regulated outletpressure of a valve assembly with the first direct acting valve in fullyor locked open state and the second direct acting valve in a modulatingstate. As can be seen in FIG. 5, the second direct acting valve caninclude a higher pressure set-point than the first direct acting valve.In other non-limiting embodiments, the second direct acting valve canhave the same or lower pressure set-point than the first direct actingvalve. As discussed above with respect to FIGS. 2A-3B, varying thegeometry of the lip element of the piston in one or both of the directacting valves can vary the set-point of the valve assembly, as shownhere in FIG. 5 as set-points C and D. Changing the geometry of first andsecond lip elements 120A and 120B of valve assembly 100, for example asdiscussed in FIGS. 3A-3B, can raise or lower set-points C and D to othertarget set-points, such as for example values ranging from approximately40 psi (276 kpa) to 65 psi (448 kpa).

An example regulated pressure P_(REG) value for set-point A includes apressure of approximately 45 psi (310 kpa) and an example for set-pointB includes a pressure of approximately 300 psi (2070 kpa). An exampleregulated pressure P_(REG) value for set-point C includes a pressure ofapproximately 40 psi (276 kpa) and an example regulated pressure P_(REG)value for set-point D includes a pressure of approximately 50 psi (345kpa). Example ranges for the axes of graph 500 include 0-350 psi(0-2,413 kpa) along the independent (e.g. horizontal axis) with regardsto valve assembly inlet pressure and 0-60 psi (0-414 kpa) along thedependent (e.g. vertical axis) with regards to the valve assembly outletpressure. An example nacelle inlet temperature value at set-point A forregulated pressure P_(REG) includes a temperature of approximately 350°F. (177° C.). An example range of normal nacelle inlet temperatures is40° to 400° F. (4.44° to 204° C.) with regards to nacelle inlettemperature, though the nacelle inlet temperature may go as high as amaximum allowable material capability such as 750° F. (399° C.) forcertain aluminum under adverse failure modes.

Additionally, as a non-limiting example, the line segments representingvalve regulated pressure P₂ and P₃ can be made up of one or more ofvarying slopes and/or curvilinear data points.

FIG. 6 is a flowchart of method 600 of regulating air pressure in ananti-icing system, for example anti-icing system 64, of an aircraft.Method 600 includes steps 602-618.

Step 602 includes flowing air into a valve assembly. The valve assemblyincludes a first direct acting valve, a first control valve assembly, asecond direct acting valve, and a second control valve assembly. Thefirst direct acting valve includes a first valve chamber and a firstpiston positioned in the first direct acting valve. The first controlvalve assembly is fluidly connected to the first valve chamber of thefirst direct acting valve. The second direct acting valve includes asecond valve chamber and a second piston positioned in the second directacting valve. The second direct acting valve is fluidly connected to thefirst direct acting valve in a series configuration. The second controlvalve assembly is fluidly connected to the second valve chamber of thesecond direct acting valve.

Controlling a heat flux of a nacelle inlet of an engine of an aircraft(collectively, step 604) includes steps 606-616. Step 606 includesadjusting at least one of the first control valve assembly and thesecond control valve assembly in response to the temperature of the airin the outlet of the second direct acting valve by controlling an amountof electrical current fed into at least one of a first solenoid valve inthe first control valve assembly and a second solenoid valve in thesecond control valve assembly. Step 608 includes adjusting a rate offlow of air released into an ambient environment external to the valveassembly out of the at least one of the first control valve assembly andthe second control valve assembly. Step 610 includes moving at least oneof the first direct acting valve and the second direct acting valve byadjusting a pressure of air in at least one of the first pressurechamber of the first direct acting valve and the second pressure chamberof the second direct acting valve. Step 612 includes adjusting a rate offlow of the air out of the valve assembly by adjusting a rate of flow ofair past the at least one of the first piston and the second piston.Step 614 includes controlling a pressure of air flowing out of an outletof the second direct acting valve in response to the adjusted rate offlow of air out of the valve assembly. Step 616 includes transportingthe air from the outlet of the valve assembly to the nacelle inlet of anengine of the aircraft.

FIG. 7 is a flowchart of method 700 of regulating air pressure in ananti-icing system, for example anti-icing system 64, of a nacelle inletof an engine of an aircraft. Method 700 includes steps 702-728. Ascompared to FIG. 6, FIG. 7 includes a non-limiting example discussingsteps for reducing a pressure of a flow of air flowing from valveassembly 100 to anti-icing system 64.

Step 702 includes flowing air into a valve assembly including first andsecond direct acting valves and first and second control valveassemblies. The first direct acting valve includes a first valvechamber, a first internal valve body surrounding the first valvechamber, and a first piston slidably engaged with the first internalvalve body. The first control valve assembly is fluidly connected to afirst valve chamber of the first direct acting valve. The first controlvalve assembly includes a first solenoid with a first ball element, afirst plunger attached to the first ball element, and a first solenoidsurrounding the first plunger, the first solenoid for creating amagnetic field to interact with the first plunger. The second directacting valve is fluidly connected to the first direct acting valve in aseries configuration. The second direct acting valve includes a secondvalve chamber, a second internal valve body surrounding the second valvechamber, and a second piston slidably engaged with the second internalvalve body. The second control valve assembly is fluidly connected to asecond valve chamber of the second direct acting valve. The secondcontrol valve assembly includes a second solenoid with a second ballelement, a second plunger attached to the second ball element, and asecond solenoid surrounding the second plunger, the second solenoid forcreating a magnetic field to interact with the second plunger.

Controlling a heat flux delivered to the nacelle inlet of an engine ofan aircraft (collectively, step 704) includes steps 706-728.

Step 706 includes energizing at least one of a first solenoid valve inthe first control valve assembly and a second solenoid valve in thesecond control valve assembly by feeding an electric current through theat least one of the first solenoid in the first control valve assemblyand the second solenoid in the second control valve assembly.

Step 708 includes increasing a rate of flow of air released into anambient environment external to the valve assembly out of at least oneof the first control valve assembly and the second control valveassembly by opening the at least one of the first solenoid valve in thefirst control valve assembly and the second solenoid valve in the secondcontrol valve assembly in response to the electric current.

Step 710 includes decreasing a pressure of air in at least one of afirst pressure chamber of the first direct acting valve and a secondpressure chamber of the second direct acting valve by decreasing apressure of the air in the at least one of the first control valveassembly and the second control valve assembly in response to theincreased rate of flow of the air released into the ambient environmentexternal to the valve assembly out of the at least one of the firstcontrol valve assembly and the second control valve assembly.

Step 712 includes moving the at least one of the first piston of thefirst direct acting valve and the second piston of the second directacting valve from an open position into a closed position such that theclosed position allows a lesser amount of air to flow past the at leastone of the first piston and second piston than the open position bydecreasing an effective area between the first internal valve body andthe first piston or between the second internal valve body and thesecond piston.

Step 714 includes passing air through a first throat formed between afirst lip element on the first piston and the first internal valve bodyof the first direct acting valve, the first lip element including afirst axial face extending at an angle θ_(LIP) between a first planeextending in an axial direction and the first axial face of the firstlip element, the first internal valve body including a first axial faceof the first internal valve body extending at an angle θ_(VB) between asecond plane extending in an axial direction and the first axial face ofthe first internal valve body, wherein an expansion angle θ_(EXP)equivalent to the difference between angle θ_(LIP) and angle θ_(VB)comprises an angle from 15° to 60°.

Step 716 includes passing air through a second throat formed between asecond lip element on the second piston and the second internal valvebody of the second direct acting valve, the second lip element includinga second axial face extending at an angle θ_(LIP) between a first planeextending in an axial direction and the second axial face of the secondlip element, the second internal valve body including a second axialface of the second internal valve body extending at an angle θ_(VB)between a second plane extending in an axial direction and the secondaxial face of the second internal valve body, wherein an expansion angleθ_(EXP) equivalent to the difference between angle θ_(LIP) and angleθ_(VB) comprises an angle from 15° to 60°.

Step 718 includes reducing a rate of flow of air past the at least oneof the first piston and the second piston in response to decreasing theeffective area between the first internal valve body and the firstpiston or between the second internal valve body and the second piston.Step 720 includes reducing a pressure of air flowing out of an outlet ofthe second direct acting valve in response to reducing the rate of flowof air past the at least one of the first piston and the second piston.Step 722 includes transporting the air from the outlet of the valveassembly to the nacelle inlet of the engine of the aircraft.

Step 724 can include at least one of steps 726 and 728. Step 726includes maintaining a temperature of the nacelle inlet surface from 40°to 400° F. (4.44° to 204° C.). Step 728 includes preventing atemperature of the nacelle inlet surface from exceeding 400° F. (204°C.).

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

An anti-icing system of a nacelle inlet of an engine of an aircraft caninclude a valve assembly fluidly connected to the nacelle inlet. Thevalve assembly can include first and second direct acting valves andfirst and second control valve assemblies. The first direct acting valvecan include a first inlet, a first valve chamber fluidly connected tothe first inlet, a first internal valve body circumferentiallysurrounding the first valve chamber, a first outlet, and/or a firstpiston for adjusting a rate of flow of air through the first directacting valve. The first piston can be slidably engaged with the firstinternal valve body. The first control valve assembly can be fluidlyconnected to the first valve chamber of the first direct acting valve.The second direct acting valve can include a second inlet, a secondvalve chamber fluidly connected to the second inlet, a second internalvalve body circumferentially surrounding the second valve chamber, asecond outlet, and/or a second piston for adjusting a rate of flow ofair through the second direct acting valve. The second piston can beslidably engaged with the second internal valve body. The second directacting valve can be fluidly connected to the first direct acting valvein a series configuration such that the second inlet of the seconddirect acting valve can be directly connected to the first outlet of thefirst direct acting valve. The second control valve assembly can befluidly connected to the second valve chamber of the second directacting valve.

The assembly of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components.

The first and second control valve assemblies can be electricallyconnected to a full authority digital engine control of the aircraft.

The first control valve assembly can comprise: a first solenoid valvewith a first ball element, a first plunger attached to or in contactwith the first ball element, and/or a first solenoid surrounding thefirst plunger, the first solenoid for creating a magnetic field tointeract with the first plunger; and/or a first pintle valve with afirst pintle housing, a first pintle disposed in the first pintlehousing, and/or a first threadably adjustable biasing element, whereinthe first pintle valve can be directly fluidly connected to the firstsolenoid valve, and/or wherein both of the first solenoid valve and thefirst pintle valve of the first control valve assembly can be fluidlyconnected to the first valve chamber of the first direct acting valve.

The second control valve assembly can comprise: a second solenoid valvewith a second ball element, a second plunger attached to the second ballelement, and/or a second solenoid surrounding the second plunger, thesecond solenoid for creating a magnetic field to interact with thesecond plunger; and/or a second pintle valve with a second pintlehousing, a second pintle disposed in the second pintle housing, and/or asecond threadably adjustable biasing element, wherein the second pintlevalve can be directly fluidly connected to the second solenoid valve,and/or wherein both of the second solenoid valve and the second pintlevalve of the second control valve assembly can be fluidly connected tothe second valve chamber of the second direct acting valve.

A first lock mechanism can be positioned in the first valve chamber ofthe first direct acting valve, the first locking mechanism can be forlocking the first piston in a fully open position, and/or a second lockmechanism positioned in the second valve chamber of the second directacting valve, the second locking mechanism can be for locking the secondpiston in a fully open position.

A first lip element can be disposed on an upstream end of the firstpiston, the first lip element can be for sealing engagement with firstinternal valve body of the first direct acting valve, wherein a firstaxial face of the first lip element can extend at an angle θ_(LIP)between a first plane extending in an axial direction and the firstaxial face of the first lip element, a first axial face of the firstinternal valve body can extend at an angle θ_(VB) between a second planeextending in an axial direction and the first axial face of the firstinternal valve body, and an expansion angle θ_(EXP) equivalent to thedifference between angle θ_(LIP) and angle θ_(VB) can comprise an anglefrom 15° to 60°.

A second lip element can be disposed on an upstream end of the secondpiston, the second lip element can be for sealing engagement with secondinternal valve body of the second direct acting valve, wherein a secondaxial face of the second lip element can extend at an angle θ_(LIP)between a first plane extending in an axial direction and the secondaxial face of the second lip element, a second axial face of the secondinternal valve body can extend at an angle θ_(VB) between a second planeextending in an axial direction and the second axial face of the secondinternal valve body, and an expansion angle θ_(EXP) equivalent to thedifference between angle θ_(LIP) and angle θ_(VB) can comprise an anglefrom 15° to 60°.

A method of regulating air pressure in an anti-icing system of a nacelleinlet of an engine of an aircraft can include flowing air into a valveassembly. The valve assembly can include first and second direct actingvalves and first and/or second control valve assemblies. The firstdirect acting valve can include a first valve chamber a first internalvalve body, and/or a first piston slidably engaged with the firstinternal valve body. The first control valve assembly can be fluidlyconnected to the first valve chamber of the first direct acting valve.The second direct acting valve can include a second valve chamber, asecond internal valve body, and/or a second piston slidably engaged withthe second internal valve body. The second direct acting valve can befluidly connected to the first direct acting valve in a seriesconfiguration. The second control valve assembly can be fluidlyconnected to the second valve chamber of the second direct acting valve.A heat flux of the nacelle inlet of the engine of the aircraft can becontrolled by the following steps. At least one of the first controlvalve assembly and the second control valve assembly can be adjusted inresponse to the temperature of the air in the outlet of the seconddirect acting valve by controlling an amount of electrical current fedinto at least one of a first solenoid valve in the first control valveassembly and a second solenoid valve in the second control valveassembly. A rate of flow of air released into an ambient environmentexternal to the valve assembly out of the at least one of the firstcontrol valve assembly and the second control valve assembly can beadjusted. At least one of the first direct acting valve and the seconddirect acting valve can be moved by adjusting a pressure of air in atleast one of the first pressure chamber of the first direct acting valveand the second pressure chamber of the second direct acting valve. Arate of flow of the air out of the valve assembly can be adjusted byadjusting a rate of flow of air past the at least one of the firstpiston and the second piston. A pressure of air flowing out of an outletof the second direct acting valve can be controlled in response to theadjusted rate of flow of air out of the valve assembly. The air from theoutlet of the valve assembly can be transported to the nacelle inlet ofthe engine of the aircraft.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components.

The at least one of the first solenoid valve in the first control valveassembly can be energized, the second solenoid valve in the secondcontrol valve assembly can be energized by feeding an electric currentthrough the at least one of the first solenoid valve in the firstcontrol valve assembly and the second solenoid valve in the secondcontrol valve assembly, the rate of flow of the air released into anambient environment external to the valve assembly out of the at leastone of the first control valve assembly and the second control valveassembly can be increased assembly by opening the at least one of thefirst solenoid valve in the first control valve assembly and the secondsolenoid valve in the second control valve assembly in response to theelectric current, the pressure of air in at least one of the firstpressure chamber of the first direct acting valve and the secondpressure chamber of the second direct acting valve can be decreased bydecreasing the pressure of air in the at least one of the first controlvalve assembly and the second control valve assembly in response to theincreased rate of flow of air released into an ambient environmentexternal to the valve assembly out of the at least one of the firstcontrol valve assembly and the second control valve assembly, the atleast one of the first piston of the first direct acting valve and thesecond piston of the second direct acting valve can be moved from anopen position into a closed position such that the closed positionallows a lesser amount of air to flow past the at least one of the firstpiston and second piston than the open position by decreasing aneffective area between the first internal valve body and the firstpiston or between the second internal valve body and the second piston,the rate of flow of air past the at least one of the first piston andthe second piston can be reduced in response to decreasing the effectivearea between the first internal valve body and the first piston orbetween the second internal valve body and the second piston, and/or thepressure of air flowing out of the outlet of the second direct actingvalve can be reduced in response to reducing the rate of flow of airpast the at least one of the first piston and the second piston.

The at least one of the first solenoid valve in the first control valveassembly and the second solenoid valve in the second control valveassembly can be de-energized by decreasing an electric current throughthe at least one of the first solenoid valve in the first control valveassembly and the second solenoid valve in the second control valveassembly, the rate of flow of the air released into an ambientenvironment external to the valve assembly out of the at least one ofthe first control valve assembly and the second control valve assemblycan be decreased by closing the at least one of the first solenoid valvein the first control valve assembly and the second solenoid valve in thesecond control valve assembly in response to the electric current, thepressure of air in at least one of the first pressure chamber of thefirst direct acting valve and the second pressure chamber of the seconddirect acting valve can be increased by increasing the pressure of airin the at least one of the first control valve assembly and the secondcontrol valve assembly in response to the decreased rate of flow of airreleased into an ambient environment external to the valve assembly outof the at least one of the first control valve assembly and the secondcontrol valve assembly, the at least one of the first piston of thefirst direct acting valve and the second piston of the second directacting valve can be moved from an closed position into a open positionsuch that the open position allows a greater amount of air to flow pastthe at least one of the first piston and second piston than the openposition by increasing an effective area between the first internalvalve body and the first piston or between the second internal valvebody and the second piston, the rate of flow of air past the at leastone of the first piston and the second piston can be increased inresponse to increasing the effective area between the first internalvalve body and the first piston or between the second internal valvebody and the second piston, and/or the pressure of air flowing out ofthe outlet of the second direct acting valve can be increased inresponse to increasing the rate of flow of air past the at least one ofthe first piston and the second piston.

The first direct acting valve and the second direct acting valve can beclosed in response to a measured temperature of the outlet of the seconddirect acting valve.

Upon a failure of the first direct acting valve, the first piston of thefirst direct acting valve can be locked in an open position.

Upon a failure of the second direct acting valve, the second piston ofthe second direct acting valve can be locked in an open position.

Air can be passed through a first throat formed between a first lipelement on the first piston and the first internal valve body of thefirst direct acting valve, the first lip element can include a firstaxial face extending at an angle θ_(LIP) between a first plane extendingin an axial direction and the first axial face of the first lip element,the first internal valve body can include a first axial face of thefirst internal valve body extending at an angle θ_(VB) between a secondplane extending in an axial direction and the first axial face of thefirst internal valve body, and an expansion angle θ_(EXP) equivalent tothe difference between angle θ_(LIP) and angle θ_(VB) can comprise anangle from 15° to 60°.

Air can be passed through a second throat formed between a second lipelement on the second piston and the second internal valve body of thesecond direct acting valve, the second lip element can include a secondaxial face extending at an angle θ_(LIP) between a first plane extendingin an axial direction and the second axial face of the second lipelement, the second internal valve body can include a second axial faceof the second internal valve body extending at an angle θ_(VB) between asecond plane extending in an axial direction and the second axial faceof the second internal valve body, and an expansion angle θ_(EXP)equivalent to the difference between angle θ_(LIP) and angle θ_(VB) cancomprise an angle from 15° to 60°.

A method of regulating air pressure in an anti-icing system of a nacelleinlet of an engine of an aircraft can include flowing air into a valveassembly. The valve assembly can include first and second direct actingvalves and first and second control valve assemblies. The first directacting valve can include a first valve chamber, a first internal valvebody surrounding the first valve chamber, and/or a first piston slidablyengaged with the first internal valve body. The first control valveassembly can be fluidly connected to a first valve chamber of the firstdirect acting valve. The first control valve assembly can include afirst solenoid with a first ball element, a first plunger attached tothe first ball element, and/or a first solenoid surrounding the firstplunger, the first solenoid can be for creating a magnetic field tointeract with the first plunger. The second direct acting valve can befluidly connected to the first direct acting valve in a seriesconfiguration. The second direct acting valve can include a second valvechamber, a second internal valve body surrounding the second valvechamber, and/or a second piston slidably engaged with the secondinternal valve body. The second control valve assembly can be fluidlyconnected to a second valve chamber of the second direct acting valve.The second control valve assembly can include a second solenoid with asecond ball element, a second plunger attached to the second ballelement, and/or a second solenoid surrounding the second plunger, thesecond solenoid for creating a magnetic field to interact with thesecond plunger. A heat flux of the nacelle inlet of the engine of theaircraft can be controlled with the following steps. At least one of afirst solenoid valve in the first control valve assembly and a secondsolenoid valve in the second control valve assembly can be energized byfeeding an electric current through the at least one of the firstsolenoid in the first control valve assembly and the second solenoid inthe second control valve assembly. A rate of flow of air released intoan ambient environment external to the valve assembly out of at leastone of the first control valve assembly and the second control valveassembly can be increased by opening the at least one of the firstsolenoid valve in the first control valve assembly and the secondsolenoid valve in the second control valve assembly in response to theelectric current. A pressure of air in at least one of a first pressurechamber of the first direct acting valve and a second pressure chamberof the second direct acting valve can be decreased by decreasing apressure of the air in the at least one of the first control valveassembly and the second control valve assembly in response to theincreased rate of flow of air released into the ambient environmentexternal to the valve assembly out of the at least one of the firstcontrol valve assembly and the second control valve assembly. The atleast one of the first piston of the first direct acting valve and thesecond piston of the second direct acting valve can be moved from anopen position into a closed position such that the closed positionallows a lesser amount of air to flow past the at least one of the firstpiston and second piston than the open position by decreasing aneffective area between the first internal valve body and the firstpiston or between the second internal valve body and the second piston.A rate of flow of air past the at least one of the first piston and thesecond piston can be reduced in response to decreasing the effectivearea between the first internal valve body and the first piston orbetween the second internal valve body and the second piston. A pressureof air flowing out of an outlet of the second direct acting valve can bereduced in response to reducing the rate of flow of air past the atleast one of the first piston and the second piston. The air from theoutlet of the valve assembly can be transported to the nacelle inlet ofthe engine of the aircraft.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components.

A temperature of the nacelle inlet surface can be maintained from 40° to400° F. (4.44° to 204° C.).

A temperature of the nacelle inlet surface can be prevented fromexceeding 400° F. (204° C.).

Air can be passed through a first throat formed between a first lipelement on the first piston and the first internal valve body of thefirst direct acting valve, the first lip element can include a firstaxial face extending at an angle θ_(LIP) between a first plane extendingin an axial direction and the first axial face of the first lip element,the first internal valve body can include a first axial face of thefirst internal valve body extending at an angle θ_(VB) between a secondplane extending in an axial direction and the first axial face of thefirst internal valve body, and an expansion angle θ_(EXP) equivalent tothe difference between angle θ_(LIP) and angle θ_(VB) can comprise anangle from 15° to 60°; and/or air can be passed through a second throatformed between a second lip element on the second piston and the secondinternal valve body of the second direct acting valve, the second lipelement can include a second axial face extending at an angle θ_(LIP)between a first plane extending in an axial direction and the secondaxial face of the second lip element, the second internal valve body caninclude a second axial face of the second internal valve body extendingat an angle θ_(VB) between a second plane extending in an axialdirection and the second axial face of the second internal valve body,and an expansion angle θ_(EXP) equivalent to the difference betweenangle θ_(LIP) and angle θ_(VB) can comprise an angle from 15° to 60°.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

The invention claimed is:
 1. An anti-icing system of a nacelle inlet ofan engine of an aircraft, wherein the anti-icing system comprises: avalve assembly fluidly connected to the nacelle inlet, wherein the valveassembly comprises: a first direct acting valve comprising: a firstinlet; a first valve chamber fluidly connected to the first inlet; afirst internal valve body circumferentially surrounding the first valvechamber, the first internal valve body having a first axial face; afirst outlet; and a first piston for adjusting a rate of flow of airthrough the first direct acting valve, wherein the first piston isslidably engaged with the first internal valve body; a first controlvalve assembly fluidly connected to the first valve chamber of the firstdirect acting valve; a second direct acting valve comprising: a secondinlet; a second valve chamber fluidly connected to the second inlet; asecond internal valve body circumferentially surrounding the secondvalve chamber; a second outlet; and a second piston for adjusting a rateof flow of air through the second direct acting valve, wherein thesecond piston is slidably engaged with the second internal valve body,and further wherein the second direct acting valve is fluidly connectedto the first direct acting valve in a series configuration such that thesecond inlet of the second direct acting valve is directly connected tothe first outlet of the first direct acting valve; and a second controlvalve assembly fluidly connected to the second valve chamber of thesecond direct acting valve; a first lip element disposed on an upstreamend of the first piston, the first lip element for sealing engagementwith first internal valve body of the first direct acting valve, whereina first axial face of the first lip element extends at an angle θ_(LIP)between a first plane extending in an axial direction and the firstaxial face of the first lip element; and wherein the first axial face ofthe first internal valve body extends at an angle θ_(VB) between asecond plane extending in an axial direction and the first axial face ofthe first internal valve body, further wherein an expansion angleθ_(EXP) equivalent to the difference between angle θ_(LIP) and angleθ_(VB) comprises an angle from 15° to 60°.
 2. The anti-icing system ofclaim 1, wherein the first and second control valve assemblies areelectrically connected to a full authority digital engine control of theaircraft.
 3. The anti-icing system of claim 1, wherein the first controlvalve assembly comprises: a first solenoid valve comprising: a firstball element; a first plunger attached to or in contact with the firstball element; and a first solenoid surrounding the first plunger, thefirst solenoid for creating a magnetic field to interact with the firstplunger; and a first pintle valve comprising: a first pintle housing; afirst pintle disposed in the first pintle housing; a first threadablyadjustable biasing element for biasing the first pintle valve, whereinthe first pintle valve is directly fluidly connected to the firstsolenoid valve, and wherein both of the first solenoid valve and thefirst pintle valve of the first control valve assembly are fluidlyconnected to the first valve chamber of the first direct acting valve.4. The anti-icing system of claim 1, wherein the second control valveassembly comprises: a second solenoid valve comprising: a second ballelement; a second plunger attached to the second ball element; and asecond solenoid surrounding the second plunger, the second solenoid forcreating a magnetic field to interact with the second plunger; and asecond pintle valve comprising: a second pintle housing; a second pintledisposed in the second pintle housing; a second threadably adjustablebiasing element for biasing the second pintle valve, wherein the secondpintle valve is directly fluidly connected to the second solenoid valve,and wherein both of the second solenoid valve and the second pintlevalve of the second control valve assembly are fluidly connected to thesecond valve chamber of the second direct acting valve.
 5. Theanti-icing system of claim 1 further comprising: a first lock mechanismpositioned in the first valve chamber of the first direct acting valve,the first locking mechanism for locking the first piston in a fully openposition; and a second lock mechanism positioned in the second valvechamber of the second direct acting valve, the second locking mechanismfor locking the second piston in a fully open position.
 6. Theanti-icing system of claim 1 further comprising: a second lip elementdisposed on an upstream end of the second piston, the second lip elementfor sealing engagement with second internal valve body of the seconddirect acting valve, wherein a second axial face of the second lipelement extends at an angle θ_(LIP) between a first plane extending inan axial direction and the second axial face of the second lip element;and a second axial face of the second internal valve body, wherein thesecond axial face of the second internal valve body extends at an angleθ_(VB) between a second plane extending in an axial direction and thesecond axial face of the second internal valve body, further wherein anexpansion angle θ_(EXP) equivalent to the difference between angleθ_(LIP) and angle θ_(VB) comprises an angle from 15° to 60°.
 7. Ananti-icing system of a nacelle inlet of an engine of an aircraft,wherein the anti-icing system comprises: a valve assembly fluidlyconnected to the nacelle inlet, wherein the valve assembly comprises: afirst direct acting valve comprising: a first inlet; a first valvechamber fluidly connected to the first inlet; a first internal valvebody circumferentially surrounding the first valve chamber; a firstoutlet; and a first piston for adjusting a rate of flow of air throughthe first direct acting valve, wherein the first piston is slidablyengaged with the first internal valve body; a first control valveassembly fluidly connected to the first valve chamber of the firstdirect acting valve; a second direct acting valve comprising: a secondinlet; a second valve chamber fluidly connected to the second inlet; asecond internal valve body circumferentially surrounding the secondvalve chamber; a second outlet; and a second piston for adjusting a rateof flow of air through the second direct acting valve, wherein thesecond piston is slidably engaged with the second internal valve body,and further wherein the second direct acting valve is fluidly connectedto the first direct acting valve in a series configuration such that thesecond inlet of the second direct acting valve is directly connected tothe first outlet of the first direct acting valve; and a second controlvalve assembly fluidly connected to the second valve chamber of thesecond direct acting valve; a second lip element disposed on an upstreamend of the second piston, the second lip element for sealing engagementwith second internal valve body of the second direct acting valve,wherein a second axial face of the second lip element extends at anangle θ_(LIP) between a first plane extending in an axial direction andthe second axial face of the second lip element; and a second axial faceof the second internal valve body, wherein the second axial face of thesecond internal valve body extends at an angle θ_(VB) between a secondplane extending in an axial direction and the second axial face of thesecond internal valve body, further wherein an expansion angle θ_(EXP)equivalent to the difference between angle θ_(LIP) and angle θ_(VB)comprises an angle from 15° to 60°.
 8. The anti-icing system of claim 7,wherein the first and second control valve assemblies are electricallyconnected to a full authority digital engine control of the aircraft. 9.The anti-icing system of claim 7, wherein the first control valveassembly comprises: a first solenoid valve comprising: a first ballelement; a first plunger attached to or in contact with the first ballelement; and a first solenoid surrounding the first plunger, the firstsolenoid for creating a magnetic field to interact with the firstplunger; and a first pintle valve comprising: a first pintle housing; afirst pintle disposed in the first pintle housing; a first threadablyadjustable biasing element for biasing the first pintle valve, whereinthe first pintle valve is directly fluidly connected to the firstsolenoid valve, and wherein both of the first solenoid valve and thefirst pintle valve of the first control valve assembly are fluidlyconnected to the first valve chamber of the first direct acting valve.10. The anti-icing system of claim 7, wherein the second control valveassembly comprises: a second solenoid valve comprising: a second ballelement; a second plunger attached to the second ball element; and asecond solenoid surrounding the second plunger, the second solenoid forcreating a magnetic field to interact with the second plunger; and asecond pintle valve comprising: a second pintle housing; a second pintledisposed in the second pintle housing; a second threadably adjustablebiasing element for biasing the second pintle valve, wherein the secondpintle valve is directly fluidly connected to the second solenoid valve,and wherein both of the second solenoid valve and the second pintlevalve of the second control valve assembly are fluidly connected to thesecond valve chamber of the second direct acting valve.
 11. Theanti-icing system of claim 7 further comprising: a first lock mechanismpositioned in the first valve chamber of the first direct acting valve,the first locking mechanism for locking the first piston in a fully openposition; and a second lock mechanism positioned in the second valvechamber of the second direct acting valve, the second locking mechanismfor locking the second piston in a fully open position.
 12. Theanti-icing system of claim 7 further comprising: a first lip elementdisposed on an upstream end of the first piston, the first lip elementfor sealing engagement with first internal valve body of the firstdirect acting valve, wherein a first axial face of the first lip elementextends at an angle θ_(LIP) between a first plane extending in an axialdirection and the first axial face of the first lip element; and a firstaxial face of the first internal valve body, wherein the first axialface of the first internal valve body extends at an angle θ_(VB) betweena second plane extending in an axial direction and the first axial faceof the first internal valve body, further wherein an expansion angleθ_(EXP) equivalent to the difference between angle θ_(LIP) and angleθ_(VB) comprises an angle from 15° to 60°.